It is well known that, an input alternating current power source should be detected in electromagnetic heating control circuits in the related art, and power of a system of an electromagnetic heating device is controlled by using a control chip or a controller to detect a voltage of an input terminal of a rectifying and filtering circuit. In the related art, the input terminal of the rectifying and filtering circuit is generally provided with a voltage sampling circuit for voltage detection. However, structures of the voltage sampling circuit are complex, thus causing high cost of circuit design and high power consumption.